Apparatus for testing adjustable resistances



May 10, 1949.

J. O. HAMILTON ET AL APPARATUS FOR TESTING ADJUSTABLE RESISTANGES Filed July 20, 1945 4 Sheets-Sheet 1 m? \l, A

Q o o o 0 0 0 0 0%) INVENTORS J 0. HAM/L TON LJ ROZA KOWSK/ A T TORNE v J. O. HAMILTON ETAL APPARATUS FOR TESTING ADJUSTABLE REISISTANCES Filed July 20, 1945 May 10, 1949.

4 Sheets-Sheet 2 /A/ V E N TORS 0. HAM/L TOA/ LJ. ROZA/VKOWSK/ A TTORNE V J. O. HAMILTON ETAL APPARATUS FOR TESTING ADJUSTABLE RESISTANCES May 10, 1949.

4 Sheets-Sheet 5 Filed July 20, 1945 @N WNYN m UP-S m Wm H M70 m mfl 0 NM 7 E T VMZ A w ,m

May 10, 1949. J. o. HAMILTON ETAL APPARATUS FOR TESTING ADJUSTABLE RESI STANCES 4 Sheets-Sheet 4 Filed July 20, 1945 NW OW vv m w 7 mmw a N 5 4, H W y 0 J L Y B m/ Patented May 10, 194 9 UNITED STATES PATENT OFFICE APPARATUS FOR TESTING ADJUSTABLE RESISTANCES James 0. Hamilton, Dundalk, and Leon J. Rolankowski, Baltimore, Md., assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application July 20, 1945, Serial No. 606,216

8 Claims. 1 This invention relates to apparatus for testing articles, and more particularly it relates to apparatus for testing the ratios of resistances of potentiometer cards.

2 ing specific embodiments thereof, when read in conjunction with the appended drawings, in which Fig. 1 is a top plan view of an apparatus for In the manufacture of potentiometers of a type testing potentiometers forming one embodiment which includes an annular potentiometer card, of the invention, with portions thereof broken a rotatable shaft mounted concentrically with reaway; spect to the potentiometer card, a brush assem- Fig. 2 is a fragmentary, vertical, partially secbly connected to the shaft for contacting the 'tional view of the apparatus; potentiometer card and a dial having a scale Fig. 3 is a fragmentary, vertical section taken formed thereon which is designed to be fastened along line 3-3 of Fig. 1; to the shaft for rotation therewith to determine Fig. 4 is a. diagrammatic view of an electrical the position of the brush assembly with respect circuit embodied in the apparatus; to the potentiometer card, it is desirable to check Fig. 5 is an enlarged, fragmentary, vertical secthe ratios of resistances of the potentiometer card tion taken along line 55 of Fig. 1; after it has been assembled in the potentiometer Fig. 6 is a fragmentary, vertical section of an but before the dial is secured to the shaft so that, apparatus forming an alternative embodiment of if the potentiometer card is defective, it may be the invention, and removed from th potentiometer and discarded i 7 iS a Or On e ti n t e alO l n without wasted effort which would be required to 1-1 of Fig. 6. mount and dismantle the dial in the potentiom- Referring now in detail to the drawings, a testeter. ing fixture It! (Figs. 1 and 2) includes a table II 'An object of the invention is the provision of having a table-top I3 made of 'wood or other suitnew and improved apparatus for testing articles. able electrical insulating material and provided Apparatus for testing potentiometers embodywith bores l6-l6 through which thumbscrews ing the invention may include means for holding l2-l2 project. The thumbscrews may be a potentiometer card of a potentiometer in a prethreaded into tapped bores HH formed in a determined position, a member having a scale base l5 of a potentiometer I! to be tested to formed thereon, a pointer positioned adjacent to secure the base in an orientated position upon the member, means for connecting the scale memthe table top l3. A pin l8 secured to the base ber toabrush assembly'of the potentiometer card at a predetermined point thereon fits into a for movement therewith, and testing means in notch l9 formed in a bracket 21 bolted'to the circuit with the potentiometer card and the brush table-top. The bracket is provided with a reassembly for determining whether ratios of relieved portion 28 to permit the base to be slid sistance of the potentiometer card obtained by under the end of the block so that the pin fits various settings of the brush assembly on the into the block. potentiometer card fall within allowable limits. Terminal posts 20, 2| and}! on the potentiom- One specific type of apparatus embodying the eter project downwardly. as viewed in Fig. 2, from invention designed for testing potentlometers the base I5 and are engaged by resilient conhaving at least one circular potentiometer card 49 tactors 24, 25 and 26, respecti e y Secured p and a rotatable brush for engaging card, comthe table-top l3. The potentiometer I1 is proprises a frame, means for supporting a potentiomvided with an annular projection 33 upon which eter in the frame, a shaft carried by the frame a ring-shaped potentiometer card 32 is mounted. in a ignment with the shaft of the potentiom- The potentiometer card 32 comprises a resistance eter, means for securing the two shafts together, wire 31 wound helically around a i 9 0f a calibrated dial secured to the shaft supported ula ng ma rial and a lead 30 connects th by e rame, and a test set for making eleczero end of the resistance wire to the terminal trical measurements upon the potentiometer, pos 0. A ead 34 connectedto the unity 6nd whereby the resistance characteristics of various of the resistance wire 3| is connected to the portions of the potentiometer card and the anguterminal post 2|. lar displacement thereof with respect to each A brush assembly 35 of the potentiometer H other may be determined. is mounted on a disc 38 which is rigidly secured Acomplete understanding of the invention may to a shaft 40 of the potentiometer. The shaft be obtained from the following detailed descrip- 40 is rotatably mounted upon the base IS in a tion of apparatus for testing potentiometers formposition in which the shaft 40 is concentric with the potentiometer card a: and may be turned to slide the brush assembly along the resistance wire 3|. A brush assembly 28 connects the brush assembly 25 to a slip ring 4|, which'is mounted rigidly upon the base I! and is insulated therefrom. A lead 42 connects the slip ring 4| to the terminal post 22.

The resilient contactors 24, 25 and 28 are connected to one end of a resistance 4 of a test set 41, the opposite end of the resistance 46 and a galvanometer 48, respectively, by conductors 42, 44 and 45, respectively. A conductor 53 connects the conductor 44 and the end of the resistance 46 to a source 50 of electrical potential, which is connected to the opposite end of the resistance 48 and the conductor 43 by conductors i4 and 56 and a manually operable switch 55 positioned therebetween. A contactor 52, which may be adjusted to contact the resistance 46 at different points thereon, is connected by a conductor 5! to the galvanometer 48.

The test set 41 serves to test the ratios of resistance of various portions of the resistance wire II with respect to the resistance of the whole of the resistance wire 3! by adjusting the contactor 52 along the resistance 48 and the contact and moving successively the brush assembly it through predetermined angles along the resistance wire ll. When the ratio of resistance of the portion of the resistance 44 between the contactor i2 and the lower end of the resistance 46 with respect to the resistance of the entire resistance 48 is equal to the ratio of resistance of the portion of the resistance wire 3| between the zero end thereof and the brush assembly I! with respect to the resistance of the entire resistance wire 2 I, no current passes through the galvanometer 48. However, if these ratios are unequal, current passes through the galvanometer 44 which indicates that condition.

A chuck 83 (Figs. 2 and 3) is splined to a shaft 64 rotatably mounted in a bearing 65 formed in a spider 68. The spider 46 is carried by posts 70-40 in a position spaced above the table-top H. A bore 41 formed in one end of the chuck receives the shaft 44, and a set screw 1| may be tightened to fasten the chuck rigidly to the shaft 64. A bore 58 formed in the other end of the chuck receives the shaft 40 of the potentiometer,

and a set screw 12 may be actuated to connect I threaded into the tapped bores 14-44 formed in the base.

A dial 7: of a large diameter has a scale 14 (Fig. 1) formed adjacent to the periphery thereof and is rigidly fastened to the shaft 5%. A vernier I5 is formed on a plate 11 secured by a thumbscrew 14 to a post 16 (Fig. 2) in a position adjacent to the periphery of the dial 13. The thumbscrew I8 passes through an arcuate slot 19 formed in the plate 11, and may be loosened to permit angular adjustment of the plate H and the vernier with respect to the dial.

A micrometer adjustment device 80 (Figs. 1 and 5) includes a spring-biased arm 8! mounting a shaft 42 having a knurled disc fastened thereto. A friction sleeve 44 mounted on the upper end of the shaft 82 normally is held'away from the pe- '4 riphery of the dial I2 by the spring-biased arm 8|. Whenthearmll is n'essedmanuallytoward the dial II and the knurled disc 42 is rotated. the shaft 42 and the friction sleeve 44 are rotated and the friction sleeve rotates the dial II and the shaft 44 slowly.

The dial Il may be secured against rotation by a clamp 40 (Figs. 1 and 2). The clamp ll includes a lever ll pivotally mounted on a frame 92 and having a clamp button 02 positioned thereon adjacent to one end. A thumbscrew l4 threaded into a tapped bore 41 formed in the other end of the lever is d to press against an abutment II of the frame 42 and pivot the lever ii in a counterclockwise direction, as viewed in Fig. 2, so as to press the clamp button '2 against the periphery of the dial II to hold the dial against rotation. A button 46 positioned on the frame 42 serves to support the dial II. The dial 13 may be released for turning movement thereof, simply by unscrewing the thumbscrew 94, which permits a leaf spring I. to press the end of the lever bearing the clamp button away from the dial. A magnifying lens I is supported by a post III in a position from which the reading of the vernier II on the scale I4 may be read through the magnifying lens.

In the operation of the testing fixture II, the set screw H is loosened, the chuck 44 is slid upwardly, as viewed in Fig. 2, upon the shaft 44, and the set screw H is tightened to secure the chuck on the shaft 44 in that pofltion. The potentiometer H is placed on the table-top IS, the pin it is slid into the notch I! formed in the bracket 21 and the base I! is pivoted about the pin until the shaft 40 is directly under the bore 44 formed in the chuck. The set screw ll then is loosened, the chuck is slid over the shaft 44, and the set screw II again is tightened to secure the chuck to the shaft 44. The chuck and the bracket now hold the potentiometer in a position in which the thumbscrews l2l2 may be threaded into the tapped bores l4-l4 formed in the base, and the terminal posts 24, 2| and 22 r are contacted by contactors 24, 25 and 24, respectively. This connects the brush assembly ii and the ends of the resistance wire II to the test set 41. The thumbscrews 12-42 then are screwed into the tapped bores, whereby the potentiometer is secured to the table-top in an orientated position with respect thereto.

The dial 12 then is rotated to a position in which the Vernier 15 reads approximately zero, and the clamp 94 is actuated to secure the dial in this position. The brush assembly 35 then is moved to the zero end of the resistance wire 30 by rotating the shaft 44 and the switch is closed to energize the test set 41 to aid in locating the brush assembly 35 on the zero end of the resistance wire. After the brush 35 is so located, and the set'screw 12 is tightened to secure the shaft 40 securely to the chuck 42 whereby the dial 13 and the brush 35 are connected for identi cal rotative movement around the axes of the shafts 64 and 44, which axes are aligned.

The thumbscrew I4 is loosened and the plate TI is adjusted with respect to the dial 13 to a position in which the vernier 14 reads exactly zero on the dial. The thumbscrew 14 then is tightened to fasten the plate 11 in this position in which the vernier is calibrated with respect to the dial.

The dial 13 then is rotated through a predetermined angle to a position in which the vernier 15 has a predetermined reading on the scale 14 (Fig. 1) formed on the dial. The brush assembly 35 rotates through a corresponding angle with that through which the dial 13 is rotated. and the contactor 52 is adjusted along the resistance 46 (Fig. 4) to a position which should correspond to the reading of the vernier 15 on the scale 14. The switch 55 (Fig. 4) then is closed and the ratio of the resistance of the portion of the resistance wire 3| between the zero end thereof and the brush assembly 35 with respect to the entire resistance of the resistance wire then'is checked to see whether it corresponds with the ratio which should be obtained from the particular setting of the brush assembly 35 and the dial 13.

The dial 131s rotated successively through predetermined angles and the test set is adjusted to check the resistance ratios for the several settings of the dial.

If the ratios of the resistance wire 3I are found to be within predetermined allowable limits, the potentiometer I'I may be removed from the fixture I and a dial (not shown) may be attached to the shaft 40 to complete the assembly of the potentiometer I1. However, if the ratios of the resistance wire 3I are not within the allowable limits, the potentiometer card 32 may be removed from the potentiometer I1 before the work in assembling the dial of the potentiometer has been. performed. Thus, a large saving in time required for assembling the potentiometers may be effected. The dial 13, which has a large diameter, the vernier 15 and the magnifying lens I00 permit the ratios of the resistance wire 3I to be read within very close limits. The bracket 21 and the chuck 13 enable an operator to quickly orient the potentiometer with respect to the fixture so that the potentiometer may be fastened thereto with no wasted effort.

A testing fixture IIO (Figs. 6 and 7) forming an alternative embodiment of the invention includes a base I II supporting a. bearing I65, which rotatably and slidably mounts a shaft I64 therein. A collar I 2I formed on the shaft I64 ordinarily rests on a shoulder I22 formed on the bearing I65. A dial I13 similar to the dial 13 (Fig. 1) and a disc I14 (Fig. 6) are fastened to the upper end of the shaft I64. A vernier I15 is positioned adjacent to the periphery of the dial I13. and a magnifying glass 200 is positioned over the vernier I15.

A member I23 fastened to the top of the dial I13 concentrically therewith has a socket I24 formed therein in which socket a split chuck I63 is mounted. A thumbscrew I12 threaded into a tapped bore I25 formed in the member I23 is designed to close the split chuck over the end of a shaft I40 of a potentiometer I I 1 so that the split chuck I63 and the shaft I40 are held concentrically against rotation relative to the member I23 and the dial I 13.

A collar I26 having a frustoconical bearing surface I21 formed thereon is fastened to the upper end of the shaft I40. A clearance bushing I28 having a frustoconical surface I29. formed.

thereon mounts the shaft I40 rotatably. The bearing surface I29 is complementary to the bearing surface I21, and centers the collar I26 and the shaft I40 when the bearing surface I21 is pressed thereagainst. The bushing I28 is. supported by a bearing I30 formed on a base I I of the potentiometer H1. The potentiometer III includes a potentiometer card I32 and a brush assembly I35. and is connected to a test set (not shown) similar to the test set 50 by suitable means (not shown).

Arms I4II4I having semicylindrical portions I42-I42 forming a clamping collar-are clamped by a bolt I43 tightly to the bearing I65. Arms,

illustrated by an arm I5I are clamped by a bolt I53 to the bearing I65, and have a yoke I54 hinged thereto by a pin I55.

Rollers I56-I56 are rotatably mounted on arms I51I51 of the yoke I54, and a cam follower I58 is mounted in a slot I59 formed in the stern of the yoke. An eccentric cam I66 fastened to a crank I61 having a handle I68 is rotatably mounted in slots I69-I69 formed in the ends of arms I4II4I. The cam I66has a lobe I10 and a depression "I formed thereon. When the cam I66 is rotated in a clockwise direction, as viewed in Fig. 6, the lobe I10 is rotated into engagement with the cam follower I58 and turns the yoke I54 in a counterclockwise direction, whereby the rollers I56--I56 raise the disc I14,

tions, as viewed in Fig. 6, to their broken-line positions.

The base II 5 of the potentiometer H1 is supported in a stationary position by a support I I2 mounted against movement on a channel II4, to which support the base is clamped by thumbscrews, illustrated by a thumbscrew II3. when the split chuck hereinabove, it slides upwardly on the shaft I40. The set screw I12 then is actuated to clamp the chuck I63 on the shaft I40, and the cam I66 is turned to move the lobe I10 out of engagement with the cam follower I58. The yoke I54 then turns by gravity in a clockwise direction, as viewed in Fig. 6, and the weight of the shaft I64, the.

eter. The brush assembly I35 and the shaft I 40 then may be rotated with respect to the base II 5 of the potentiometer and the dial I13 rotates therewith.

In the operation of the testing fixture III), the base II5 of the potentiometer H1 is placed upon the support H2, and is clamped thereon by the thumbscrews illustrated by the thumbscrew H3. The dial I13 is moved approximately to zero with respect to the vernier I15 and the brush assembly I35 is positioned in engagement with the zero end of the resistance card I32, a test set (not shown) similar to the test set 35 (Fig. 1) being used to check the position of the brush assembly I35 (Fig. 6) on the potentiometer card I32. The crank I61 is turned from its full-line position to its broken-line position, and the dial I13, the shaft I 64, the member I23 and the split chuck I63 are raised by the yoke I54, which is turned by the cam I66.

The chuck I63 then is tightened on the shaft I40 by the thumbscrew I12 and the crank I61 is turned to its full-line position leaving the chuck I63, the member I23, the dial I13, the disc I14 and the shaft I64 suspended from the shaft I 40. The vernier I15 then is adjusted to read zero on the dial I13, and the potentiometer card I32 then 7 Thus, I 63 is raised, as described operation with the bracket, the potentiometer in a predetermined position in the fixture.

8. In a testing apparatus including a test set for testing a resistance wire of an annular potentiometer card of a potentiometer having a base provided with pin, a shaft rotatably mounted on the base and a brush assembly carried by the shaft for slidably engaging the resistance wire, a fixture which comprises a support, a block secured to the support in a predetermined position thereon and provided with a notch for receiving the pin projecting from the base of the potentiometer, a dial, a shaft rigidly fastened to the dial for mounting it rotatably, means for' mounting the dial-mounting shaft for rotation, a double-ended chuck mounted slidably on the dial-mounting shaft, means for securing the chuck to the shaft of the potentiometer to 10- cate, in cooperation with the bracket, the potentiometer in a predetermined position on the support, and a plurality of thumbscrews for securing the base of the potentiometer to the support in that position.

, JAMES O. HAMILTON.

LEON J. ROZANKOWSKI,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,808,777 Jones June 9, 1931 1,846,153 Sherman Feb. 23, 1932 1,870,462 McWeeny Aug. 9, 1932 1,966,066 Haskins July 10, 1934 2,052,688 Allen Sept. 1, 1938 2,390,840 Koren Dec. 11, 1945 

